Single-photon emission computed tomography

Last updated
Single-photon emission computed tomography
SPECT Slice of Brain using Tc-99m Ceretec.jpg
A SPECT slice of the distribution of technetium exametazime within a patient's brain
ICD-9-CM 92.0-92.1
MeSH D01589
OPS-301 code 3-72
SPECT image (bone tracer) of a mouse MIP Mouse02-spect.gif
SPECT image (bone tracer) of a mouse MIP
Collimator used to collimate gamma rays (red arrows) in a gamma camera Lead collimator.svg
Collimator used to collimate gamma rays (red arrows) in a gamma camera

Single-photon emission computed tomography (SPECT, or less commonly, SPET) is a nuclear medicine tomographic imaging technique using gamma rays. [1] It is very similar to conventional nuclear medicine planar imaging using a gamma camera (that is, scintigraphy), [2] but is able to provide true 3D information. This information is typically presented as cross-sectional slices through the patient, but can be freely reformatted or manipulated as required.

Contents

The technique needs delivery of a gamma-emitting radioisotope (a radionuclide) into the patient, normally through injection into the bloodstream. On occasion, the radioisotope is a simple soluble dissolved ion, such as an isotope of gallium(III). Usually, though, a marker radioisotope is attached to a specific ligand to create a radioligand, whose properties bind it to certain types of tissues. This marriage allows the combination of ligand and radiopharmaceutical to be carried and bound to a place of interest in the body, where the ligand concentration is seen by a gamma camera.

Principles

A Siemens brand SPECT scanner, consisting of two gamma cameras. TEMP-Siemens.jpg
A Siemens brand SPECT scanner, consisting of two gamma cameras.

Instead of just "taking a picture of anatomical structures", a SPECT scan monitors level of biological activity at each place in the 3-D region analyzed. Emissions from the radionuclide indicate amounts of blood flow in the capillaries of the imaged regions. In the same way that a plain X-ray is a 2-dimensional (2-D) view of a 3-dimensional structure, the image obtained by a gamma camera is a 2-D view of 3-D distribution of a radionuclide.

SPECT imaging is performed by using a gamma camera to acquire multiple 2-D images (also called projections), from multiple angles. A computer is then used to apply a tomographic reconstruction algorithm to the multiple projections, yielding a 3-D data set. This data set may then be manipulated to show thin slices along any chosen axis of the body, similar to those obtained from other tomographic techniques, such as magnetic resonance imaging (MRI), X-ray computed tomography (X-ray CT), and positron emission tomography (PET).

SPECT is similar to PET in its use of radioactive tracer material and detection of gamma rays. In contrast with PET, the tracers used in SPECT emit gamma radiation that is measured directly, whereas PET tracers emit positrons that annihilate with electrons up to a few millimeters away, causing two gamma photons to be emitted in opposite directions. A PET scanner detects these emissions "coincident" in time, which provides more radiation event localization information and, thus, higher spatial resolution images than SPECT (which has about 1 cm resolution). SPECT scans are significantly less expensive than PET scans, in part because they are able to use longer-lived and more easily obtained radioisotopes than PET.

Because SPECT acquisition is very similar to planar gamma camera imaging, the same radiopharmaceuticals may be used. If a patient is examined in another type of nuclear medicine scan, but the images are non-diagnostic, it may be possible to proceed straight to SPECT by moving the patient to a SPECT instrument, or even by simply reconfiguring the camera for SPECT image acquisition while the patient remains on the table.

SPECT machine performing a total body bone scan. The patient lies on a table that slides through the machine, while a pair of gamma cameras rotate around her. SPECT CT.JPG
SPECT machine performing a total body bone scan. The patient lies on a table that slides through the machine, while a pair of gamma cameras rotate around her.

To acquire SPECT images, the gamma camera is rotated around the patient. Projections are acquired at defined points during the rotation, typically every 3–6 degrees. In most cases, a full 360-degree rotation is used to obtain an optimal reconstruction. The time taken to obtain each projection is also variable, but 15–20 seconds is typical. This gives a total scan time of 15–20 minutes.

Multi-headed gamma cameras can accelerate acquisition. For example, a dual-headed camera can be used with heads spaced 180 degrees apart, allowing two projections to be acquired simultaneously, with each head requiring 180 degrees of rotation. Triple-head cameras with 120-degree spacing are also used.

Cardiac gated acquisitions are possible with SPECT, just as with planar imaging techniques such as multi gated acquisition scan (MUGA). Triggered by electrocardiogram (EKG) to obtain differential information about the heart in various parts of its cycle, gated myocardial SPECT can be used to obtain quantitative information about myocardial perfusion, thickness, and contractility of the myocardium during various parts of the cardiac cycle, and also to allow calculation of left ventricular ejection fraction, stroke volume, and cardiac output.

Application

SPECT can be used to complement any gamma imaging study, where a true 3D representation can be helpful, such as tumor imaging, infection (leukocyte) imaging, thyroid imaging or bone scintigraphy.

Because SPECT permits accurate localisation in 3D space, it can be used to provide information about localised function in internal organs, such as functional cardiac or brain imaging.

Myocardial perfusion imaging

Myocardial perfusion imaging (MPI) is a form of functional cardiac imaging, used for the diagnosis of ischemic heart disease. The underlying principle is that under conditions of stress, diseased myocardium receives less blood flow than normal myocardium. MPI is one of several types of cardiac stress test.

A cardiac specific radiopharmaceutical is administered, e.g., 99mTc-tetrofosmin (Myoview, GE healthcare), 99m Tc-sestamibi (Cardiolite, Bristol-Myers Squibb) or Thallium-201 chloride. Following this, the heart rate is raised to induce myocardial stress, either by exercise on a treadmill or pharmacologically with adenosine, dobutamine, or dipyridamole (aminophylline can be used to reverse the effects of dipyridamole).

SPECT imaging performed after stress reveals the distribution of the radiopharmaceutical, and therefore the relative blood flow to the different regions of the myocardium. Diagnosis is made by comparing stress images to a further set of images obtained at rest which are normally acquired prior to the stress images.

MPI has been demonstrated to have an overall accuracy of about 83% (sensitivity: 85%; specificity: 72%) (in a review, not exclusively of SPECT MPI), [3] and is comparable with (or better than) other non-invasive tests for ischemic heart disease.

Functional brain imaging

Usually, the gamma-emitting tracer used in functional brain imaging is Technetium (99mTc) exametazime. 99mTc is a metastable nuclear isomer that emits gamma rays detectable by a gamma camera. Attaching it to exametazime allows it to be taken up by brain tissue in a manner proportional to brain blood flow, in turn allowing cerebral blood flow to be assessed with the nuclear gamma camera.

Because blood flow in the brain is tightly coupled to local brain metabolism and energy use, the 99mTc-exametazime tracer (as well as the similar 99mTc-EC tracer) is used to assess brain metabolism regionally, in an attempt to diagnose and differentiate the different causal pathologies of dementia. Meta-analysis of many reported studies suggests that SPECT with this tracer is about 74% sensitive at diagnosing Alzheimer's disease vs. 81% sensitivity for clinical exam (cognitive testing, etc.). More recent studies have shown the accuracy of SPECT in Alzheimer's diagnosis may be as high as 88%. [4] In meta analysis, SPECT was superior to clinical exam and clinical criteria (91% vs. 70%) in being able to differentiate Alzheimer's disease from vascular dementias. [5] This latter ability relates to SPECT's imaging of local metabolism of the brain, in which the patchy loss of cortical metabolism seen in multiple strokes differs clearly from the more even or "smooth" loss of non-occipital cortical brain function typical of Alzheimer's disease. Another recent review article showed that multi-headed SPECT cameras with quantitative analysis result in an overall sensitivity of 84-89% and an overall specificity of 83-89% in cross sectional studies and sensitivity of 82-96% and specificity of 83-89% for longitudinal studies of dementia. [6]

99mTc-exametazime SPECT scanning competes with fludeoxyglucose (FDG) PET scanning of the brain, which works to assess regional brain glucose metabolism, to provide very similar information about local brain damage from many processes. SPECT is more widely available, because the radioisotope used is longer-lasting and far less expensive in SPECT, and the gamma scanning equipment is less expensive as well. While 99mTc is extracted from relatively simple technetium-99m generators, which are delivered to hospitals and scanning centers weekly to supply fresh radioisotope, FDG PET relies on FDG, which is made in an expensive medical cyclotron and "hot-lab" (automated chemistry lab for radiopharmaceutical manufacture), and then delivered immediately to scanning sites because of the natural short 110-minute half-life of Fluorine-18.

Applications in nuclear technology

In the nuclear power sector, the SPECT technique can be applied to image radioisotope distributions in irradiated nuclear fuels. [7] Due to the irradiation of nuclear fuel (e.g. uranium) with neutrons in a nuclear reactor, a wide array of gamma-emitting radionuclides are naturally produced in the fuel, such as fission products (cesium-137, barium-140 and europium-154) and activation products (chromium-51 and cobalt-58). These may be imaged using SPECT in order to verify the presence of fuel rods in a stored fuel assembly for IAEA safeguards purposes, [8] to validate predictions of core simulation codes, [9] or to study the behavior of the nuclear fuel in normal operation, [10] or in accident scenarios. [11]

Reconstruction

SPECT Sinogram SPECT Sinogram 360.jpg
SPECT Sinogram

Reconstructed images typically have resolutions of 64×64 or 128×128 pixels, with the pixel sizes ranging from 3–6 mm. The number of projections acquired is chosen to be approximately equal to the width of the resulting images. In general, the resulting reconstructed images will be of lower resolution, have increased noise than planar images, and be susceptible to artifacts.

Scanning is time-consuming, and it is essential that there is no patient movement during the scan time. Movement can cause significant degradation of the reconstructed images, although movement compensation reconstruction techniques can help with this. A highly uneven distribution of radiopharmaceutical also has the potential to cause artifacts. A very intense area of activity (e.g., the bladder) can cause extensive streaking of the images and obscure neighboring areas of activity. This is a limitation of the filtered back projection reconstruction algorithm. Iterative reconstruction is an alternative algorithm that is growing in importance, as it is less sensitive to artifacts and can also correct for attenuation and depth dependent blurring. Furthermore, iterative algorithms can be made more efficacious using the Superiorization methodology. [12]

Attenuation of the gamma rays within the patient can lead to significant underestimation of activity in deep tissues, compared to superficial tissues. Approximate correction is possible, based on relative position of the activity, and optimal correction is obtained with measured attenuation values. Modern SPECT equipment is available with an integrated X-ray CT scanner. As X-ray CT images are an attenuation map of the tissues, this data can be incorporated into the SPECT reconstruction to correct for attenuation. It also provides a precisely registered CT image, which can provide additional anatomical information.

Scatter of the gamma rays as well as the random nature of gamma rays can also lead to the degradation of quality of SPECT images and cause loss of resolution. Scatter correction and resolution recovery are also applied to improve resolution of SPECT images. [13]

Typical SPECT acquisition protocols

Study Radioisotope Emission energy (keV) Half-life Radiopharmaceutical Activity (MBq)Rotation (degrees)ProjectionsImage resolutionTime per projection (s)
Bone scan technetium-99m 1406 hoursPhosphonates / Bisphosphonates800360120128 x 12830
Myocardial perfusion scan technetium-99m1406 hourstetrofosmin; Sestamibi 7001806064 x 6425
Sestamibi parathyroid scan technetium-99m1406 hours Sestamibi
Brain scantechnetium-99m1406 hoursTc exametazime; ECD555-111036064128 x 12830
Neuroendocrine or neurological tumor scan iodine-123 or iodine-131 15913 hours or 8 days MIBG 4003606064 x 6430
White cell scan indium-111 & technetium-99m171 & 24567 hoursin vitro labelled leucocytes183606064 x 6430

SPECT/CT

In some cases a SPECT gamma scanner may be built to operate with a conventional CT scanner, with coregistration of images. As in PET/CT, this allows location of tumors or tissues which may be seen on SPECT scintigraphy, but are difficult to locate precisely with regard to other anatomical structures. Such scans are most useful for tissues outside the brain, where location of tissues may be far more variable. For example, SPECT/CT may be used in sestamibi parathyroid scan applications, where the technique is useful in locating ectopic parathyroid adenomas which may not be in their usual locations in the thyroid gland. [14]

Quality control

The overall performance of SPECT systems can be performed by quality control tools such as the Jaszczak phantom. [15]

See also

Related Research Articles

<span class="mw-page-title-main">Positron emission tomography</span> Medical imaging technique

Positron emission tomography (PET) is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes, and in other physiological activities including blood flow, regional chemical composition, and absorption. Different tracers are used for various imaging purposes, depending on the target process within the body.

<span class="mw-page-title-main">Nuclear medicine</span> Medical specialty

Nuclear medicine or nucleology is a medical specialty involving the application of radioactive substances in the diagnosis and treatment of disease. Nuclear imaging, in a sense, is "radiology done inside out" because it records radiation emitted from within the body rather than radiation that is transmitted through the body from external sources like X-ray generators. In addition, nuclear medicine scans differ from radiology, as the emphasis is not on imaging anatomy, but on the function. For such reason, it is called a physiological imaging modality. Single photon emission computed tomography (SPECT) and positron emission tomography (PET) scans are the two most common imaging modalities in nuclear medicine.

A radioactive tracer, radiotracer, or radioactive label is a synthetic derivative of a natural compound in which one or more atoms have been replaced by a radionuclide. By virtue of its radioactive decay, it can be used to explore the mechanism of chemical reactions by tracing the path that the radioisotope follows from reactants to products. Radiolabeling or radiotracing is thus the radioactive form of isotopic labeling. In biological contexts, experiments that use radioisotope tracers are sometimes called radioisotope feeding experiments.

Technetium (<sup>99m</sup>Tc) sestamibi Pharmaceutical drug

Technetium (99mTc) sestamibi (INN) is a pharmaceutical agent used in nuclear medicine imaging. The drug is a coordination complex consisting of the radioisotope technetium-99m bound to six (sesta=6) methoxyisobutylisonitrile (MIBI) ligands. The anion is not defined. The generic drug became available late September 2008. A scan of a patient using MIBI is commonly known as a "MIBI scan".

<span class="mw-page-title-main">Scintigraphy</span> Diagnostic imaging test in nuclear medicine

Scintigraphy, also known as a gamma scan, is a diagnostic test in nuclear medicine, where radioisotopes attached to drugs that travel to a specific organ or tissue (radiopharmaceuticals) are taken internally and the emitted gamma radiation is captured by gamma cameras, which are external detectors that form two-dimensional images in a process similar to the capture of x-ray images. In contrast, SPECT and positron emission tomography (PET) form 3-dimensional images and are therefore classified as separate techniques from scintigraphy, although they also use gamma cameras to detect internal radiation. Scintigraphy is unlike a diagnostic X-ray where external radiation is passed through the body to form an image.

<span class="mw-page-title-main">Perfusion</span> Passage of fluid through the circulatory or lymphatic system to an organ or tissue

Perfusion is the passage of fluid through the circulatory system or lymphatic system to an organ or a tissue, usually referring to the delivery of blood to a capillary bed in tissue. Perfusion may also refer to fixation via perfusion, used in histological studies. Perfusion is measured as the rate at which blood is delivered to tissue, or volume of blood per unit time per unit tissue mass. The SI unit is m3/(s·kg), although for human organs perfusion is typically reported in ml/min/g. The word is derived from the French verb "perfuser" meaning to "pour over or through". All animal tissues require an adequate blood supply for health and life. Poor perfusion (malperfusion), that is, ischemia, causes health problems, as seen in cardiovascular disease, including coronary artery disease, cerebrovascular disease, peripheral artery disease, and many other conditions.

<span class="mw-page-title-main">Bone scintigraphy</span> Nuclear medicine imaging technique

A bone scan or bone scintigraphy is a nuclear medicine imaging technique of the bone. It can help diagnose a number of bone conditions, including cancer of the bone or metastasis, location of bone inflammation and fractures, and bone infection (osteomyelitis).

<span class="mw-page-title-main">Neuroimaging</span> Set of techniques to measure and visualize aspects of the nervous system

Neuroimaging is the use of quantitative (computational) techniques to study the structure and function of the central nervous system, developed as an objective way of scientifically studying the healthy human brain in a non-invasive manner. Increasingly it is also being used for quantitative research studies of brain disease and psychiatric illness. Neuroimaging is highly multidisciplinary involving neuroscience, computer science, psychology and statistics, and is not a medical specialty. Neuroimaging is sometimes confused with neuroradiology.

<span class="mw-page-title-main">Technetium-99m</span> Metastable nuclear isomer of technetium-99

Technetium-99m (99mTc) is a metastable nuclear isomer of technetium-99, symbolized as 99mTc, that is used in tens of millions of medical diagnostic procedures annually, making it the most commonly used medical radioisotope in the world.

<span class="mw-page-title-main">Myocardial perfusion imaging</span> Nuclear medicine imaging method

Myocardial perfusion imaging or scanning is a nuclear medicine procedure that illustrates the function of the heart muscle (myocardium).

<span class="mw-page-title-main">Octreotide scan</span> Type of medical imaging

An octreotide scan is a type of SPECT scintigraphy used to find carcinoid, pancreatic neuroendocrine tumors, and to localize sarcoidosis. It is also called somatostatin receptor scintigraphy (SRS). Octreotide, a drug similar to somatostatin, is radiolabeled with indium-111, and is injected into a vein and travels through the bloodstream. The radioactive octreotide attaches to tumor cells that have receptors for somatostatin. A gamma camera detects the radioactive octreotide, and makes pictures showing where the tumor cells are in the body, typically by a SPECT technique. A technetium-99m based radiopharmaceutical kit is also available.

Perfusion is the passage of fluid through the lymphatic system or blood vessels to an organ or a tissue. The practice of perfusion scanning is the process by which this perfusion can be observed, recorded and quantified. The term perfusion scanning encompasses a wide range of medical imaging modalities.

Nuclear medicine physicians, also called nuclear radiologists or simply nucleologists, are medical specialists that use tracers, usually radiopharmaceuticals, for diagnosis and therapy. Nuclear medicine procedures are the major clinical applications of molecular imaging and molecular therapy. In the United States, nuclear medicine physicians are certified by the American Board of Nuclear Medicine and the American Osteopathic Board of Nuclear Medicine.

Rubidium-82 (82Rb) is a radioactive isotope of rubidium. 82Rb is widely used in myocardial perfusion imaging. This isotope undergoes rapid uptake by myocardiocytes, which makes it a valuable tool for identifying myocardial ischemia in Positron Emission Tomography (PET) imaging. 82Rb is used in the pharmaceutical industry and is marketed as Rubidium-82 chloride under the trade names RUBY-FILL and CardioGen-82.

Emission computed tomography (ECT) is a type of tomography involving radioactive or emissions. Types include positron emission tomography (PET) and Single-photon emission computed tomography (SPECT).

<span class="mw-page-title-main">Cardiac imaging</span>

Cardiac imaging refers to minimally invasive imaging of the heart using ultrasound, magnetic resonance imaging (MRI), computed tomography (CT), or nuclear medicine (NM) imaging with PET or SPECT. These cardiac techniques are otherwise referred to as echocardiography, Cardiac MRI, Cardiac CT, Cardiac PET and Cardiac SPECT including myocardial perfusion imaging.

<span class="mw-page-title-main">Brain positron emission tomography</span> Form of positron emission tomography

Brain positron emission tomography is a form of positron emission tomography (PET) that is used to measure brain metabolism and the distribution of exogenous radiolabeled chemical agents throughout the brain. PET measures emissions from radioactively labeled metabolically active chemicals that have been injected into the bloodstream. The emission data from brain PET are computer-processed to produce multi-dimensional images of the distribution of the chemicals throughout the brain.

Preclinical or small-animal Single Photon Emission Computed Tomography (SPECT) is a radionuclide based molecular imaging modality for small laboratory animals. Although SPECT is a well-established imaging technique that is already for decades in use for clinical application, the limited resolution of clinical SPECT (~10 mm) stimulated the development of dedicated small animal SPECT systems with sub-mm resolution. Unlike in clinics, preclinical SPECT outperforms preclinical coincidence PET in terms of resolution and, at the same time, allows to perform fast dynamic imaging of animals.

Philip F. Cohen is a Canadian clinical director of Nuclear Medicine working out of the Lions Gate Hospital in North Vancouver, British Columbia. As a nuclear medicine physician, he is a pioneer in the usage of 3-D imaging techniques to improve diagnosis of bone disease and injury in collaboration with the Medical Imaging Research Group at University of British Columbia. Furthermore, Cohen has been involved in clinical research trials of new radiopharmaceuticals. To that effect, Cohen was the first recipient of a research grant from the Lions Gate Hospital Foundation, one of several peer-reviewed awards that would follow.

<span class="mw-page-title-main">Oxygen-15 labelled water</span> Chemical compound

Oxygen-15 labelled water (also known as 15O-water, [O-15]-H2O, or H215O) is a radioactive variation of regular water, in which the oxygen atom has been replaced by oxygen-15 (15O), a positron-emitting isotope. 15O-water is used as a radioactive tracer for measuring and quantifying blood flow using positron emission tomography (PET) in the heart, brain and tumors.

References

  1. ↑ SPECT at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
  2. ↑ Scuffham J W (2012). "A CdTe detector for hyperspectral SPECT imaging". Journal of Instrumentation. IOP Journal of Instrumentation. 7 (8): P08027. doi:10.1088/1748-0221/7/08/P08027. S2CID   250665467.
  3. ↑ Elhendy, A; Bax, JJ; Poldermans, D (2002). "Dobutamine stress myocardial perfusion imaging in coronary artery disease". Journal of Nuclear Medicine. 43 (12): 1634–46. PMID   12468513.
  4. ↑ Bonte FJ, Harris TS, Hynan LS, Bigio EH, White CL (2006). "Tc-99m exametazime SPECT in the differential diagnosis of the dementias with histopathologic confirmation". Clin Nucl Med. 31 (7): 376–8. doi:10.1097/01.rlu.0000222736.81365.63. PMID   16785801. S2CID   39518497.
  5. ↑ Dougall NJ, Bruggink S, Ebmeier KP (2004). "Systematic review of the diagnostic accuracy of 99mTc-HMPAO-SPECT in dementia". Am J Geriatr Psychiatry. 12 (6): 554–70. doi:10.1176/appi.ajgp.12.6.554. PMID   15545324.
  6. ↑ Henderson, Theodore (December 2012). "The diagnosis and evaluation of dementia and mild cognitive impairment with emphasis on SPECT perfusion neuroimaging". CNS Spectrums. 17 (4): 188–89. doi:10.1017/S1092852912000636. PMID   22929226. S2CID   36441907.
  7. ↑ Jacobsson Svärd, Staffan (2004). A tomographic measurement technique for irradiated nuclear fuel assemblies. Uppsala: Acta Universitatis Upsaliensis. ISBN   9155459447.
  8. ↑ Levai, F; Dési, S; Tarvainen, M; Artt, R (1993). Use of high energy gamma emission tomography for partial defect verification of spent fuel assemblies. Helsinki: Finnish Centre for Radiation and Nuclear Safety. ISBN   9514779754.
  9. ↑ Jacobsson Svärd Staffan, Håkansson Ane, Bäcklin Anders, Osifo Otasowie, Willman Christopher, Jansson Peter (2005). "Nondestructive Experimental Determination of the Pin-Power Distribution in Nuclear Fuel Assemblies". Nuclear Technology. 151 (1): 70–76. Bibcode:2005NucTe.151...70S. doi:10.13182/NT05-A3632. S2CID   98426662.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  10. ↑ Andersson P (2017). "A computerized method (UPPREC) for quantitative analysis of irradiated nuclear fuel assemblies with gamma emission tomography at the Halden reactor". Annals of Nuclear Energy. 110: 88–97. doi:10.1016/j.anucene.2017.06.025.
  11. ↑ Biard B (2013). "Quantitative analysis of the fission product distribution in a damaged fuel assembly using gamma-spectrometry and computed tomography for the Phébus FPT3 test". Nuclear Engineering and Design. 262: 469–483. doi:10.1016/j.nucengdes.2013.05.019.
  12. ↑ Luo, S, Zhou, T (2014). "Superiorization of EM algorithm and its application in single-photon emission computed tomography (SPECT)". Inverse Problems and Imaging. 8: 88–97. arXiv: 1209.6116 . doi:10.3934/ipi.2014.8.223. S2CID   119657086.
  13. ↑ "D. Boulfelfel, R.M. Rangayyan, L.J. Hahn, R. Kloiber, Restoration of Single Photon Emission Computed Tomography Images" . Retrieved 10 January 2016.
  14. ↑ Neumann DR, Obuchowski NA, Difilippo FP (2008). "Preoperative 123I/99mTc-sestamibi subtraction SPECT and SPECT/CT in primary hyperparathyroidism". J Nucl Med. 49 (12): 2012–7. doi: 10.2967/jnumed.108.054858 . PMID   18997051.
  15. ↑ Jennifer Prekeges. Nuclear Medicine Instrumentation. Jones & Bartlett Publishers. 2012. ISBN   1449645372 p.189

Further reading

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.